Apparatus for classifying fragments of tobacco

ABSTRACT

Apparatus for segregating relatively light shredded tobacco leaf laminae from heavier particles of tobacco ribs and stem has a feeding device which showers a mixture of lighter and heavier particles onto the upper stretch of a rapidly moving classifying belt which propels the particles beyond one of its ends whereby the heavier particles are segregated from lighter particles because their flight span is longer than that of the shreds. The lighter particles are thereupon spread apart by a battery of horizontal winnowers of rectangular cross-sectional outline which distribute such particles on the upper stretch of a collecting belt which moves counter to the direction of travel of the upper stretch of the classifying belt. The feeding device has a carded belt which transports a sliver of intermixed lighter and heavier particles and from which a picker roller removes successive increments of the sliver to shower the particles onto the upper stretch of the classifying belt. The heavier particles are collected in a trough and are evacuated by a rotating screw.

United States Patent 1 91 David etal. 1 1 Sept. 11, 1973 54] APPARATUSFOR CLASSIFYING 550,101 11/1895 Flanegin 131/109 R ux FRAGMENTS 0FTOBACCO FOREIGN PATENTS OR AlPPLlCATlONS [75] Inventors: Harry David,Hamburg; Willy 887,496 l/1962 Great Britain 131 109 R Rudszinat,Dassendorf, both of 240,574 11/1911 Germany 131/109 R Germany [73]Assignee: Hanne-Werke Korher & Co. KG,

Hamburg, Germany [22] Filed: Dec. 15, 1970 [21] Appl. No.: 98,349

[30] Foreign Application Priority Data Dec. 22, 1969 Great Britain62,446/69 {52] US. Cl. 131/109 B, 131/21 A, 131/21 B, 1 209/120, 131/110[51] Int. Cl. A24c 1/02 [58] Field of Search 131/108, 109 R, 109 AB,131/109 B, 110, 146, 120; 209/120 [56] References Cited UNlTED STATESPATENTS 2,151,527 3/1939 Podmore 131/146 UX 2,230,195 l/l941 Warren131/109 B 1,326,547 12/1919 Teale 131/109 B 2,212,265 8/1940 Downing,.lr. 209/120 2,211,096 8/1940 Brown 209/120 X 716,449 12/1902 MacDonald131/109 R UX 406,611 7/1889 Allison 131/109 R UX 2,731,673 1/1956Wallace 131/110 X Primary Examiner Joseph S. Reich Attorney-Michael S.Striker [57] ABSTRACT Apparatus for segregating relatively lightshredded tobacco leaf laminae from heavier particles of tobacco ribs andstem has a feeding device which showers a mixture of lighter and heavierparticles onto the upper stretch of a rapidly moving classifying beltwhich propels the particles beyond one of its ends whereby the heavierparticles are segregated from lighter particlesbecause their flight spanis longer than that of the shreds. The lighter particles are thereuponspread apart by a battery of horizontal winnowers of rectangularcross-sectional outline which distribute such particles on the upperstretch of a collecting belt which moves counter to the direction oftravel of the upper stretch of the classifying belt. The feeding devicehas a carded belt which transports a sliver of intermixed lighter andheavier particles and from which a picker roller removes successiveincrements of the sliver to shower the particles onto the upper stretchof the classifying belt. The heavier particles are collected in a troughand are evacuated by a rotating screw.

9 Claims, 1 Drawing Figure PATENTED 1 1975 3.757. 800

m M m wall-r Raga/"' A TTORNEV APPARATUS FOR CLASSIFYING FRAGMENTS OFTOBACCO BACKGROUND OF THE INVENTION The present invention relates toapparatus for segregating lighter particles from a mixture of lighterand heavier particles, particularly for segregating shreds of tobaccoleaf laminae from a mixture which contains such shreds in randomdistribution with fragments of tobacco ribs, stem, birds eyes and/orother heavier tobacco particles.

It is already known to segregate lighter and heavier tobacco particlesby showering a mixture of such particles onto one or more rapidlyrotating winnowers which are intended to propel the heavier particlesalong first paths and the lighter particles along second paths to thuseffect a separation of lighter and heavier particles. As a rule, thewinnowers are rollers which are provided with outwardly extendingprojections in the form of strips, ribs, vanes, blades or the like. Theprojections prevent the winnowers from propelling all lighter particlesin a first direction and all heavier particles in a second direction sothat the classifying action is not entirely satisfactory and theresulting accumulations or batches which respectively contain the majorpart of lighter and heavier particles must be subjected to one or moresecondary classifying actions. Furthermore, the force with which theparticles are propelled by different portions of such winnowers varieswithin a wide range which also contributes to an unsatisfactoryclassifying action. The flight spans of ligher particles are often aslong as the flight spans of heavier particles, i.e., such flight spansare not determined exclusively by the specific weight of particlesand/or by the resistance which the particles offer to propulsion throughthe surrounding air.

SUMMARY OF THE INVENTION An object of the invention is to provide anovel and improved apparatus for segregating lighter particles which areintermixed with heavier particles, particularly for segregating shredsof tobacco leaf laminae from fragments of tobacco ribs, stem or birdseyes in such a way that all or nearly all lighter particles areeffectively separated from heavier particles in a single separating orclassifying zone.

Another object of the invention is to provide the apparatus with noveland improved winnowers.

A further object of the invention is to provide the apparatus with noveland improved means for propelling a mixture of lighter and heavierparticles in such a way that all or nearly all lighter particles areimmediately and effectively segregated from the heavier particles.

An additional object of the invention is to provide an apparatus whichis particularly suited for segregating from a mixture of lighter andheavier tobacco particles those particles which can be immediatelyintroduced into a-machine for making a continuous filler stream to beused in the manufacture of wrapped tobacco rod sections.

The improved apparatus comprises a classifying conveyor including anendless flexible belt having a particle supporting and advancingstretch, drive means for rapidly moving the stretch lengthwise in apredetermined direction, a feeding device for continuously supplying tothe stretch a mixture of randomly distributed lighter and heavierparticles which form on the stretch a layer advancing with and beyondthe downstream end of the stretch whereby the flight span of heavierparticles is longer than the flight span of lighter particles so thatthe lighter particles are effectively separated from the heavierparticles, and means for collecting the thus separated lighter particlesindependently of the heavier particles.

The apparatus further preferably comprises a rotary pressing memberwhich overlies and rests on the layer of intermixed particles close tothe downstream end of the stretch of the classifying conveyor, and abattery of preferably parallel rotary spreading members of winnowerswhich are located in the path of lighter particles leaving theclassifying conveyor and serve to distribute the lighter particles overa substantial part of the collecting means. Each winnower is preferablyof polygonal, most preferably of rectangular cross-sectional outline.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved classifying apparatus itself, however, both as to itsconstruction and its mode of operation, together with additionalfeatures and advantages thereof, will be best understood upon perusal ofthe following detailed description of certain specific embodiments withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE is a schematic sideelevational view of a distributor which serves to supply tobacco shredsto a cigarette rod making machine and comprises a classifying apparatuswhich embodies the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates adistributor for a cigarette making machine. The purpose of thedistributor is to withdraw fragmentized tobacco leaves from a large ormain supply l and to convert the thus withdrawn mixture of lighter andheavier tobacco particles into a uniform narrow tobacco filler stream 3which is ready for wrapping into cigarette paper without trimming orafter trimming. The resulting wrapped tobacco filler rod is thereuponsevered to yield plain cigarettes of desired length. The main supply 1contains interlaced tobacco shreds and heavier particles which may ormay not form coherent clumps or batches. The conversion of particleswhich are withdrawn from the main supply 1 into the filler stream 3takes place in several stages including the formation of a uniformsilver or carpet 2 which is thereupon relieved of heavier particles 2ato form a carpet 2b. The latter is converted into the tiller stream 3.The main supply 1 is replenished with fragmentized tobacco which issupplied by a pneumatic delivery hopper 6.

The main supply 1 is stored in a container 4 which is located below theoutlet of the delivery hopper 6. The intermixed lighter and heavierparticles which are withdrawn from the main supply I are accumulatedinto several smaller supplies or piles including a relatively I smalllast or final supply 7 and three intermediate supplies 8, 9 and 11. Thequantity of tobacco particles in each of the intermediate supplies 8, 9,11 is less than in the main supply 1 (when the latter contains a maximumquantity of particles) but exceeds the quantity of particles in the lastsupply 7. The means for transporting tobacco particles between theintermediate supplies 8, 9, 11 as well as to and away from the finalsupply 7 comprises an endless conveyor belt 13 provided with a cardingl2 and trained over rollers 14, 16, 17 at least one of which is driven,preferably at a constant speed, to advance the particles in thedirection indicated by arrows.

A lifting conveyor 18 includes an endless belt 23 trained over rollers19, 21 at least one of which is driven at a variable speed so that thecarding 22 on the right-hand stretch of the belt 23 transports acontinuous layer of particles past a tobacco leveling refuser wheel 28having a set of elastic tongues or blades 27.

' The thus equalized layer is beaten out of the carding 22 by a rotatingpicker or comb-off roller 26 which propels the removed particles into afunnel-shaped receptacle 24 for the first or largest intermediate supply11. That stretch of the conveyor belt 13 which extends between therollers 16 and 17 constitutes a moving wall of the receptacle 24. Thepicker roller 26 can be replaced with a rotary brush or the like. Theparts 18, 26 and 28 together constitute a withdrawing unit which drawsfrom the main supply 1 a substantially uniform layer of tobaccoparticles for delivery to the first intermediate supply 11.

The receptacle 24 accommodates or supports a level detector or indicatorincluding one or more light sources (not shown) and one or morephotosensitive receivers 29 which produce signalswhenever theintermediate supply 11 in the receptacle 24 rises to a predeterminedmaximum permissible level or descends below a minimum permissible level.The illustrated receiver 29 is connected with the input of a regulatingunit 31 which serves to vary the speed of the conveyor belt 23 so as tomaintain the amount of tobacco particles in the intermediate supply 11within a desired range. The regulating unit 31 comprises a time delayrelay 32, a preamplifier 33 which is in series with the relay 32, apower output amplifier 34 which is in series with the preamplifier 33,and a variable-speed electric motor 36 which drives the roller 21 forthe belt 23.

The means for removing a uniform sliver 2 of tobacco particles from thelast supply 7 comprises the upper stretch of the belt 13 on which thesupply 7 rests and a tobacco leveling refuser wheel 35 which isanalogous to the refuser wheel 28. The sliver 2 is removed from the belt13 by a rotating picker roller or removing roller 40 (which can bereplaced with a rotating brush) whereby the particles of the sliver 2are showered onto a classifying conveyor 189 here shown as including anendless belt 89 trained over rollers 87, 88. The roller 87 is driven ata high speed by a shaft 87a so that the particle supporting andadvancing upper stretch 89a of the belt 89 travels in the directionindicated by an arrow F.

The means for removing a layer of tobacco particles from the firstintermediate supply 11 comprises the aforementioned inclined stretch ofthe belt 13 (between the rollers 16 and 17) and a rotary refuser wheel47 which is preferably identical with the wheels 28, 35 and returns theexcess of particles back into the receptacle 24. The thus equalizedlayer is fed to the second intermediate supply 9 which is supported bythe upper stretch of the belt 13 and from which such upper stretchwithdraws a continuous layer which is equalized by a refuser wheel 46.The equalized layer which is permitted to advance beyond the refuserwheel 46 is admitted to the third intermediate supply 8 which rests onthe upper stretch of the belt 13 between the supplies 7 and 9. The upperstretch of the belt 13 cooperates with a further refuser wheel 44 towithdraw from the supply 8 a continuous layer of tobacco particles whichare admitted to the last layer 7.

The supplies 7, 8, 9 are respectively located below level indicators ordetectors each of which includes at least one light source (not shown)and at least one photosensitive receiver 37, 38, 39, respectively. Theillustrated receiver 37 is connected with the input ofa regulating unit41 which serves to adjust the refuser wheel 44 and to thus regulate thethickness of the layer which is being withdrawn from the lastintermediate supply 8. The regulating unit 41 comprises a time delayrelay 48, an amplifier 49 and a servomotor 51 which can move the refuserwheel 44 toward or away from the upper stretch of the belt 13, dependingupon whether the amount of tobacco in the last supply 7 is above amaximum permissible level or below a minimum permissible level. Thedetector including the receiver 37 is perferably a so-called maximum andminimum level indicator which can transmit appropriate signals inresponse to depletion of the supply 7 to a minimum permissible level andin response to a rise of the supply 7 beyond a maximum permissiblelevel. In this way, the supply 7 invariably contains an amount oftobacco particles which is within a desired range.

The level indicators including the photoelectric receivers 38, 39 arepreferably identical with the level indicator for the last supply 7. Thereceiver 38 is connected with the input of a regulating unit 42 having atime delay relay 52, an amplifier 54 and a servomotor 57 which can movethe refuser wheel 46 toward or away from the upper stretch of the belt13 to thereby control the amount of tobacco particles in the lastintermediate supply 8.

The receiver 39 is connected with the input ofa regulating unit 43 whichincludes a time delay relay 53, an amplifier 56 and a servomotor 58which can move the refuser wheel 47 toward or away from the adjacentinclined stretch of the belt 13 to thereby insure that the amount oftobacco particles in the second intermediate supply 9 remains within adesired range. The means for rotating the refuser wheels 28, 47, 46, 44,35, the picker rollers 26, 40, and at least one of the rollers l4, 16,17 is not shown in FIG. 1. The servomotors 51, 57, 58 preferably includeelectromagnets whose armatures are coupled to the driven shafts of therespective refuser wheels and can move such shafts sideways (toward oraway from the adjacent stretches of the belt 13) with reference tosuitable guides, not shown. It is clear, however, that the servomotors51, 57, 58 may comprise variable-speed electric motors which can shiftthe refuser wheels through the intermediary of suitable transmissions sothat the shaft of each adjustable refuser wheel can be moved sidewaysbetween a finite or infinite number of positions. All that counts is toprovide the distributor with means which can regulate the rate oftransport of tobacco particles between successive supplies 1, ll, 9, 8and 7.

The upper stretch 89a of the belt 89 accumulates a layer 2' whoseparticles are advanced in the direction indicated by the arrow F to bepropelled, beyond the end turn at the roller 88 (which is rotated in thedirection indicated by the arrow D) so that the heavier particles 2a(for example, those consisting of fragments of ribs, stern and/orso-called birds eyes) are propelled into a collecting trough 94acontaining a rotary evacuating conveyor here shown as a screw 94. Theflight span of heavier particles 2a is longer than the flight span oflighter particles 2b which descend into a spreading zone A containingthree parallel horizontal rotary spreading members or winnowers 91, 92,93 of polygonal (preferably rectangular) cross-sectional outline. Thewinnowers 91-93 distribute the lighter particles 2b on the upper stretch95a of an endlessbelt 95 whereon such particles form a wide carpet 2b ofuniform height and width. Such carpet is transported in the directionindicated .by the arrow G and its particles are showered in astream-forming zone H to enter a guide channel 98 which accumulates theaforementioned filler stream 3. The character 8 denotes the dischargeend of the stretch 89a where the heavier particles 2a are automaticallyseparated from the lighter particles 2b. The endless belt 95 forms partof a collecting conveyor 195 for tobacco shreds.

A pressing roller 90 is mounted on a pivotable lever 90a and rests onthe layer 2 at a level above the roller 88. The roller 90 is an idlerroller and the direction of its rotation is indicated by an arrow C,i.e., the rollers 88, 90 rotate in opposite directions. The winnowers91-93 rotate in directions indicated by arrows E, namely, counter to thedirection of rotation of the roller 89. The belt 95 is trained overrollers 96, 97 the latter of which is driven, preferably at a constantspeed, by a shaft 97a. The width of the guide channel 98 decreases in adownward direction, and its bottom wall supports a narrow endless tapeorband 99 which transports the filler stream 3 lengthwise (at right anglesto the plane of FIG. 1) toward a wrapping and rod forming-mechanism ofconventional design.

It will be noted that the direction of rotation of the winnowers 91-93(arrows E) is counter to the direction of rotation (arrow D) of theroller 88. Also, the direction of travel of the upper stretch 89a (arrowF) is counter to the direction of travel of the upper stretch 95a (arrowG). This reduces the overall length of the classifying apparatus whosefeeding device includes the carded belt 13 and the removing roller 40.The stretches 89a, 95a and the axes of the winnowers 91-93 arepreferably located in horizontal planes.

The pressing roller 90 can be biased against the upper side of the layer2' by one or more springs 90b or the like.

The operation:

The delivery hopper 6 admits a mixture of lighter and heavier tobaccoparticles into the container 4 so that the latter accumulates a mainsupply 1 wherein the particles are interlaced and normally form at leastsome batches of coherent particles. The motor 36 is started to drive thebelt23 of the lifting conveyor 18 so that the carding22 draws from thesupply 1 a continuous layer which is equalized by the refuser wheel 28and removed from. thecarding by the picker roller 26 to enter thereceptacle 24 where it accumulates to form the first intermediate supply11. When the supply 11 rises to the level of the photosensitive receiver29, the latter produces a signal which causes the power output amplifier34 in the regulating unit 31 to receive little or no current whereby thevariable-speed motor 36 is either idle or drives the roller 21 at a lowspeed. The time delay relay 32 insures that the speed of the motor 36 isnot changed in response to short-lasting interruptions of the light beambetween the light source and the receiver 29, for example, in responseto such interruptions which are caused by tobacco particles showeredinto the receptacle 24 by the picker roller 26.

The belt 13 is driven at a constant speed and its inclined stretch drawsfrom the intermediate supply 1] a continuous layer of particles which isequalized by the refuser wheel 47 and is advanced by the upper stretchof the belt 13 to form the intermediate supplies 9, 8 and the lastsupply 7. As shown in FIG. 1, the supply8 contains more tobacco than thesupply 7 but less tobacco than the supply 9. The latter contains lesstobacco than.

the supply 11. Once the upper stretch of the belt 13 accumulates thesupplies 9, 8 and 7, it begins to draw from the last supply 7 acontinuous and substantially uniform homogeneous sliver 2 which isremoved by the picker roller 40 and is showered continuously onto theupper stretch 89a of the belt 89.

The level indicators including the receivers 37, 38, 39 respectivelyscan the supplies 7,8, 9 and initiate adjustments in the position of therefuser wheel 44, 46

and/or an when the amount of tobacco particles in the correspondingsupply rises above or decreases below a permissible value. The receiver29 scans the intermediate supply 11 and initiates adjustments in thespeed of the motor 36 and thus insure that the amount of tobaccoparticles in the receptacle 24 does not rise above or decrease below apermissible range. As mentioned above, the level indicators whichinclude the receivers 37, 38, 39 are preferably desired to move thecorresponding refuser wheels toward or away from the adjacent portionsof the belt 13.

The classifying belt 89 of the conveyor 189 is, driven by the shaft 87aat a relatively high speed so as to move its upper stretch 89a in thedirection indicated by the arrow F whereby the inertia of the heavierparticles 2a causes such particles to travel against the thread of thescrew 94 which moves them to a collecting or further processing station.The separation of heavier particles 2a from the lighter particles 2btakes place at the discharge end B of the stretch 89a (immediatelydownstream of the pressing roller 90) and the lighter particles 2b enterthe spreading zone A tobe distributed by the winnowers 91-93 and to formon the upper stretch 95a of the collecting belt 95 a wide and homogenouscarpet 2b which is transported in the direction indicated by the arrowG. The lighter particles 2b contain mainly fragments or shreds oftobacco leaf laminae.

The purpose of the pressing roller 90 is to insure, in cooperation withthe roller 88, that the lighter and heavier particles 21;, 2a whichreach the discharge end 8 travel at the same speed and in the samedirection. Thus, the parts 88, 90 cooperate to guarantee that theparticles 2a, 2b will travel along different paths solely as a result ofdifferences in their nature to thus insure a highly accurate classifyingaction between ribs, stern and birds eyes on the one hand and fragmentsor shreds of tobacco leaf laminae on the other hand.

The winnowers 91-93 bring about further homogenization of lightweightmaterial which is discharged from the stretch 89a of the classifyingbelt 89 and enters the spreading zone A. Consequently, the carpet 2bcontains uniformly distributed lighter particles which can be showeredinto the guide channel 98 toform on the tape 99 a narrow fillerstream 3which can be introduced into a wrapping mechanism.

An advantage of the structure which supplies particles of tobacco to thecarded belt 13 and of the feeding device including the belt 13 and thepicker roller 40 is that the upper stretch 89a of the belt 89 receives astream of loose particles which can be readily segregated into lighterand heavier particles. It was found that the segregation which iscarried out downstream of the discharge end of the stretch 89a is verysatisfactory for the formation of a filler stream 3 which containsshreds of tobacco leaf laminae. It was further found that the polygonalwinnowers 91-93 are much more satisfactory than presently known bladedor ribbed winnowers. The winnowers 9l-93 need not segregate lighterparticles 212 from the heavier particles 2a; they serve to insuresatisfactory distribution of lighter particles on the particleintercepting upper stretch 95a of the collecting belt 95.

Withoutfurther analysis, the foregoing will so fully reveal the gist ofthe present invention that others can,

I by applying current knownledge, readily adapt it for variousapplications without omitting features which fairly constitute essentialcharacteristics of the generic and specific aspects of our contributionto the art and, therefore, such adaptations should and are intended tobe comprehended within the meaning and range of equivalence of theclaims.

What is claimed as new and desired to be protected by Letters Patent isset forth'in the appended claims:

1. Apparatus for segregating lighter and heavier tobacco particles whichform a mixture of such particles, particularly for segregating particlesof 'ribs and stem from shreds of tobacco leaf laminae, comprising aclassifying conveyor including a plurality of rotary elements and anendless flexible belt trained over said rotary elements and having aparticle supporting and advancing upper stretch, said upper stretchhaving a discharge end; drive means for moving said upper stretchlengthwise; a feeding device including a conveyor arranged to accumulateand transport a sliver consisting of a mixture of lighter and heaviertobacco particles and to supply such mixture to said upper stretchwhereon the lighter and heavier particles form a layer advancing towardand beyond said discharge end and into a spreading zone locateddownstream of said upper stretch; a rotary member located in the regionof said discharge end and opposite said upper stretch so as to engage atleast some of the particles on said upper stretch and to be rotatedthereby so that rotation of said rotary member together with movement ofsaid upper stretch of said endless flexible belt cause propulsion of alltobacco particles into said spreading zone at a predetermined speedwhereby the flight span of the heavier particles is longer than theflight span of lighter particles with attendant separation of lighterand heavier particles; first collecting means for collecting the thusseparated lighter particles, including a conveyor having a movingintercepting portion arranged to collect the separated ligher particlesin the form of a carpet; and second collecting means for collecting theseparated heavier particles.

2. Apparatus as defined in claim 1, wherein said elements are rollers,one of said rollers being adjacent to said discharge end and said rotarymember overlying the layer on said stretch in the region of said oneroller.

3. Apparatus as defined in claim 2, wherein said rotary member ismounted to ride on said layer.

4. Apparatus as defined in claim 1, further comprising spreading meansinterposed in said spreading zone in the path of lighter particlesbetween said classifying conveyor and said first collecting means todistribute the lighter particles over a substantial part of saidintercepting portion.

5. Apparatus as defined in claim 4, wherein said spreading meanscomprises a battery of rotary spreading members.

6. Apparatus as defined in claim 5, wherein said spreading members arewinnowers each having a polygonal cross-sectional outline.

7. Apparatus as defined in claim 5, wherein said upper stretch of saidbelt is located in a first substantially horizontal plane and the axesof said spreading members are located in a second substantiallyhorizontal plane, said intercepting portion for separated lighterparticles being located in a third substantially horizontal plane.

8. Apparatus as defined in claim 7, wherein said conveyor of said firstcollecting means comprises a second endless belt having an upper stretchwhich constitutes said intercepting portion, and drive means for movingsaid last mentioned upper stretch in a direction counter to thedirection of movement of said upper stretch of said first mentionedbelt.

9. Apparatus as defined in claim 8, wherein one of said rotary elementscomprises a roller adjacent to said discharge, said roller beingarranged to rotate in a first direction and said spreading members beingarranged to rotate in a second direction.

1. Apparatus for segregating lighter and heavier tobacco particles whichform a mixture of such particles, particularly for segregating particlesof ribs and stem from shreds of tobacco leaf laminae, comprising aclassifying conveyor including a plurality of rotary elements and anendless flexible belt trained over said rotary elements and having aparticle supporting and advancing upper stretch, said upper stretchhaving a discharge end; drive means for moving said upper stretchlengthwise; a feeding device including a conveyor arranged to accumulateand transport a sliver consisting of a mixture of lighter and heaviertobacco particles and to supply such mixture to said upper stretchwhereon the lighter and heavier particles form a layer advancing towardand beyond said discharge end and into a spreading zone locateddownstream of said upper stretch; a rotary member located in the regionof said discharge end and opposite said upper stretch so as to engage atleast some of the particles on said upper stretch and to be rotatedthereby so that rotation of said rotary member together with movement ofsaid upper stretch of said endless flexible belt cause propulsion of alltobacco particles into said spreading zone at a predetermined speedwhereby the flight span of the heavier particles is longer than theflight span of lighter particles with attendant separation of lighterand heavier particles; first collecting means for collecting the thusseparated lighter particles, including a conveyor having a movingintercepting portion arranged to collect the separated ligher particlesin the form of a carpet; and second collecting means for collecting theseparated heavier particles.
 2. Apparatus as defined in claim 1, whereinsaid elements are rollers, one of said rollers being adjacent to saiddischarge end and said rotary member overlying the layer on said stretchin the region of said one roller.
 3. Apparatus as defined in claim 2,wherein said rotary member is mounted to ride on said layer. 4.Apparatus as defined in claim 1, further comprising spreading meansinterposed in said spreading zone in the path of lighter particlesbetween said classifying conveyor and said first collecting means todistribute the lighter particles over a substantial part of saidintercepting portion.
 5. Apparatus as defined in claim 4, wherein saidspreading means comprises a battery of rotary spreading members. 6.Apparatus as defined in claim 5, wherein said spreading members arewinnowers each having a polygonal cross-sectional outline.
 7. Apparatusas defined in claim 5, wherein said upper stretch of said belt islocated in a first substantially horizontal plane and the axes of saidspreading members are located in a second substantially horizontalplane, said intercepting portion for separated lighter particles beinglocated in a third substantially horizontal plane.
 8. Apparatus asdefined in claim 7, wherein said conveyor of said first collecting meanscomprises a second endless belt having an upper stretch whichconstitutes said intercepting portion, and drive means for moving saidlast mentioned upper stretch in a direction counter to the direction ofmovement of said upper stretch of said first mentioned belt. 9.Apparatus as defined in claim 8, wherein one of said rotary elementscomprises a roller adjacent to said discharge, said roller beingarranged to rotate in a first direction and said spreading members beingarranged to rotate in a second direction.